1. Field of the Invention
The present invention relates to an electronic component mounting apparatus for picking and placing electronic components to a circuit board and a method of replacing a nozzle in the electronic component mounting apparatus.
2. Description of the Related Art
Electronic component mounting apparatuses pick up electronic components stored in a component feeder with their head nozzle vacuum-sucking electronic components and bring and mount them on a circuit board that is positioned at a predetermined place. The component feeder holds electronic components of a variety of types in a wide range of size, and its feeding head automatically changes its nozzle in accordance with the type of the electronic component to be picked up. The electronic component mounting apparatus is therefore provided with a nozzle stocker which stocks a diversity of nozzles. The feeding head moves above the nozzle stocker and is then vertically lowered and raised to replace automatically its nozzle.
To replace the head, the feeding head is shifted over the nozzle stocker, and is lowered and then raised while the nozzle used is removed from a nozzle mount to be returned back into the nozzle stocker, and a new nozzle is taken by mounting it on the nozzle mount. There are times when the head fails to return its used nozzle in a correct alignment into the nozzle stocker with the nozzle left elevated from the nozzle stocker.
Japanese Unexamined Patent Publication 2-132897 and Japanese Unexamined Patent Publication 4-188742 disclose units that detect such an error in the returning action of nozzle. In these disclosures, a holder that houses nozzles is equipped with a number of light emitting devices and light receiving devices facing nozzles. Light emitted by the light emitting devices is received by the light receiving devices and an error, if any, in the nozzle returning action is then detected.
In the prior art, however, light emitting devices and light receiving devices are required for the respective nozzles, increasing the count of the devices, making the wiring of the devices complicated and thereby pushing up the cost of the unit.